Best Mate, one of the finest jumpers in horse racing history, has died after suffering a heart attack following a race at Exeter this afternoon.

The horse, which won three Cheltenham Gold Cups in a stellar career, was returning to the track for the first time this season in the William Hill Haldon Gold Cup. Jockey Paul Carberry tracked the leader Ashley Brook for the first half of the race, but he started to nudge the horse on as the leaders moved clear. Carberry began to ease him in the home straight, eventually pulling him up, and screens were swiftly put up around him.

Best Mate's trainer Henrietta Knight said: "I have ridden a horse before who suffered a heart attack while I was on board and I have to say this looks reminiscent of that. The legs go, they wobble and then they go down. I was actually on the track where he came down and I was the first one there. I knew immediately he had died.

"As I saw him go down I knew I was seeing a dead horse and I just wanted it to be over as quickly as possible. I am very proud of him - he looked an absolute picture today on a course he loved. He was a joy to work with and a privilege to train.

"Obviously I am very sorry for the jockey and for Mr and Mrs Lewis, who are distraught. It is probably harder for a lot of people watching the race than it is for Terry and I, as we are more used to this sort of thing happening.

"He was a very, very popular horse with a tremendous following and now there is a big vacuum. Even this morning he was getting good luck cards in the post - but I suppose we have all got to go one day and at least he didn't do anything terrible like fall or break a leg. We will all miss him very much."

Terry Biddlecombe, Knight's husband, added: "Paul is a good jockey and he knew something was wrong. The only consolation is it was pretty instantaneous and he wouldn't have felt any pain."

Best Mate had been forced to miss an attempt at a fourth consecutive Gold Cup when he burst a blood vessel in his final workout before the big race. He had not raced in public since finishing second in Ireland last Christmas, but connections had reported that all had been well with the 10-year-old in his preparations for his reappearance.

The Grade Two contest went to the Philip Hobbs-trained Monkerhostin (10-1), who romped away under Richard Johnson to a comfortable four-length success over Kauto Star.